HEMATOLOGY AND BIOCHEMISTRY REFERENCE VALUES IN NESTLING RED KITES (MILVUS MILVUS) IN SHORT-TERM HUMAN CARE IN ENGLAND

Between the years 2022 and 2023, 62 red kite (Milvus milvus) nestlings were translocated from England to Spain to bolster declining populations in mainland Europe as part of a wider conservation initiative. Health examinations were undertaken by veterinarians ahead of translocation, including examination of hematology and biochemistry parameters from blood samples. This study aimed to establish reference values for these parameters in nestling red kites for use in future translocations or for other clinical purposes. All individuals included in the analysis were clinically healthy at the time of sampling. Biochemical reference intervals were comparable to published values for other Accipitridae, although differences in hematology were noted: PCV was generally lower; and WBC counts higher than (up to triple) those reported for related species of a similar age. It is hypothesized that these differences reflect species variations or the effects of the stress of recent capture on the immune system of the red kites. A Leucocytozoon species was identified on blood smears of six of the red kites. The reference intervals presented in this study are representative of free-living red kite nestlings in England that have recently been captured for conservation translocation purposes.

Ecological time lags in biodiversity response to habitat changes

The decline of biodiversity can occur with a substantial delay following habitat loss, degradation, and other environmental changes, such as global warming. Considerable time lags may be involved in these responses. However, such time lags typically pose a significant but often unrecognized challenge for biodiversity conservation across a wide range of taxa and ecosystems. Here, we synthesize the current knowledge, categories, manifestations under different scenarios and impacts of ecological time lags. Our work reveals that studies on ecosystem structure lags are far more than ecosystem process and function lags. Due to the presence of these time-lag effects, the 'window phase' typically exists, which is widely recognized as 'relaxation time', providing a particular opportunity for biodiversity conservation. The manifestations of time lags vary under different scenarios. In addition, the different mechanisms that can result in ecological time lags are hierarchically nested, in which mechanisms at the population and metapopulation level have routinely been suggested as explanations for ecological time lags. It generally takes longer time to reach equilibrium at the metapopulation level than it takes for effects to be fully expressed at the level of individuals. Finally, we propose corresponding implications for biodiversity conservation and management. Our research will provide priorities for science and management on how to address the impact of ecological time lags to mitigate future attrition of biodiversity.

Hardship at birth alters the impact of climate change on a long-lived predator

Climate change is increasing the frequency of extreme events, such as droughts or hurricanes, with substantial impacts on human and wildlife communities. Extreme events can affect individuals through two pathways: by altering the fitness of adults encountering a current extreme, and by affecting the development of individuals born during a natal extreme, a largely overlooked process. Here, we show that the impact of natal drought on an avian predator overrode the effect of current drought for decades, so that individuals born during drought were disadvantaged throughout life. Incorporation of natal effects caused a 40% decline in forecasted population size and a 21% shortening of time to extinction. These results imply that climate change may erode populations more quickly and severely than currently appreciated, suggesting the urgency to incorporate “penalties” for natal legacies in the analytical toolkit of impact forecasts. Similar double impacts may apply to other drivers of global change.

The long-term effects of extreme climate events in early life are largely overlooked in forecasts of climate change impacts. Here, the authors show that raptorial red kites born during drought are disadvantaged throughout life, and including this climate legacy leads to substantial decreases in forecasted population size and time to extinction.

Enhancing monitoring and transboundary collaboration for conserving migratory species under global change: The priority case of the red kite

Calls for urgent action to conserve biodiversity under global change are increasing, and conservation of migratory species in this context poses special challenges. In the last two decades the Convention on the Conservation of Migratory Species of Wild Animals (CMS) has provided a framework for several subsidiary instruments including action plans for migratory bird species, but the effectiveness and transferability of these plans remain unclear. Such laws and policies have been credited with positive outcomes for the conservation of migratory species, but the lack of international coordination and on-ground implementation pose major challenges. While research on migratory populations has received growing attention, considerably less emphasis has been given to integrating ecological information throughout the annual cycle for examining strategies to conserve migratory species at multiple scales in the face of global change. We fill this gap through a case study examining the ecological status and conservation of a migratory raptor and facultative scavenger, the red kite (Milvus milvus), whose current breeding range is limited to Europe and is associated with agricultural landscapes and restricted to the temperate zone. Based on our review, conservation actions have been successful at recovering red kite populations within certain regions. Populations however remain depleted along the southern-most edge of the geographic range where many migratory red kites from northern strongholds overwinter. This led us to a forward-looking and integrated strategy that emphasizes international coordination involving researchers and conservation practitioners to enhance the science-policy-action interface. We identify and explore key issues for conserving the red kite under global change, including enhancing conservation actions within and outside protected areas, recovering depleted populations, accounting for climate change, and transboundary coordination in adaptive conservation and management actions. The integrated conservation strategy is sufficiently general such that it can be adapted to inform conservation of other highly mobile species subject to global change.

Demographic modeling to fine-tune conservation targets: importance of pre-adults for the decline of an endangered raptor

Large, long-lived species with slow life histories and protracted pre-breeding stages are particularly susceptible to declines and extinction, often for unknown causes. Here, we show how demographic modeling of a medium-sized raptor, the Red Kite Milvus milvus, can aid to refocus conservation research and attention on the most likely mechanisms driving its decline. Red Kites' survival and reproduction increased through three sequential stages for 1-2, 3-6, and 7-30 yr of age, mainly corresponding to individuals that are dispersing, attempting to gain a territory, and breeding. As typical of long-lived species, elasticities were highest for adult (≥7 yr old) survival, but this was high, with little scope for improvement. Instead, the declines were driven by an extremely low survival of pre-adults in their first years of life, which weakened the whole demographic system by nullifying the offspring contribution of adults and curtailing their replacement by recruits. For example, 27 pairs were necessary to generate a single prime age adult. Simulation of management scenarios suggested that the decline could be halted most parsimoniously by increasing pre-adult survival to the mean levels recorded for other areas, while only the synergistic, simultaneous improvement of breeding success, adult and pre-adult survival could generate a recovery. We propose three actions to attain such goals through selective supplementary feeding of both breeding and non-breeding individuals, and through mortality improvement by GPS remote-sensing devices employed as surveillance monitoring tools. Our results show how improving demographic models by using real, local vital rates rather than "best guess" vital rates can dramatically improve model realism by refocusing attention on the actual stages and mortality causes in need of manipulation, thus building precious time and resources for conservation management. These results also highlight the frequent key role of pre-adult survival for the management of long-lived species, coherent with the idea of demographic systems as integrated chains only as strong as their weakest link.

Direct evidence of poison-driven widespread population decline in a wild vertebrate

Toxicants such as organochlorine insecticides, lead ammunition, and veterinary drugs have caused severe wildlife poisoning, pushing the populations of several apex species to the edge of extinction. These prime cases epitomize the serious threat that wildlife poisoning poses to biodiversity. Much of the evidence on population effects of wildlife poisoning rests on assessments conducted at an individual level, from which population-level effects are inferred. Contrastingly, we demonstrate a straightforward relationship between poison-induced individual mortality and population changes in the threatened red kite (Milvus milvus). By linking field data of 1,075 poisoned red kites to changes in occupancy and abundance across 274 sites (10 × 10-km squares) over a 20-y time frame, we show a clear relationship between red kite poisoning and the decline of its breeding population in Spain, including local extinctions. Our results further support the species listing as endangered, after a breeding population decline of 31% to 43% in two decades of this once-abundant raptor. Given that poisoning threatens the global populations of more than 2,600 animal species worldwide, a greater understanding of its population-level effects may aid biodiversity conservation through increased regulatory control of chemical substances. Our results illustrate the great potential of long-term and large-scale on-ground monitoring to assist in this task.

Avian Scavengers as Bioindicators of Antibiotic Resistance due to Livestock Farming Intensification

Industrial food animal production uses huge amounts of antibiotics worldwide. Livestock, their excreta used for manure and meat subproducts not intended for human consumption can all play important roles in the transmission of bacterial resistance to wildlife. Vultures and other scavengers can be directly exposed to active antibiotics ingested while feeding on livestock carcasses. This study evaluates whether bacterial resistance in the red kite (Milvus milvus) differs between two wintering areas selected based on patent differences in farming practices—particularly in the industrial production of food animals (primarily swine and poultry) vs. scarce and declining sheep herding. The results support the hypothesis that intensification in food animal production is associated with increased bacterial multidrug resistance in wildlife. Resistance was positively correlated with time elapsed since the beginning of the commercial application of each antibiotic in human and veterinary medicine, with clear differences depending on farming intensification between areas. Monitoring programs are encouraged to use red kites and other avian scavengers as valuable sentinels of contamination by antibiotics and clinically relevant resistant pathogens from livestock operations of variable intensities. Farms authorized for supplementary feeding of threatened scavengers should avoid supplying carcasses with active antibiotic residues to avoid bacterial resistance in scavenger wildlife.